head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Execution · Practiced Mastery
Linear sci-fi shooting plus spatial puzzles with fixed solutions.

Execution · Pure Mechanics
Wrestling motion-control aim and swordplay through fixed scripted shootouts.
Prey leans Execution (Practiced Mastery); Red Steel leans Execution (Pure Mechanics).
Red Steel leans a little harder on execution, though the gap is small.
Prey
Standard FPS aim with portal disorientation added
Red Steel
Wiimote aiming and sword swings are the whole physical test
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Prey
Alien enemies follow fixed scripts
Red Steel
Enemies are scripted spawns, never adaptive
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Prey
Linear campaign with little randomness
Red Steel
Encounters are fixed once seen
Prey leans a little harder on optimization, though the gap is small.
Prey
Portal and gravity puzzles have fixed solutions
Red Steel
Light level memorisation and weapon choices
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.